How did the FBI find the Silk Road server, really?

Fascinating piece on how the FBI found the Silk Road server and thus its owner, or rather, if there was foul play involved in the discovery.

The FBI also provided the defense with the traffic logs from the Silk Road server, but Weaver didn’t like the look of those either. He suggested that the logs didn’t show the FBI getting an IP address from a leaky CAPTCHA, but a PHPMyAdmin configuration page.

So now another question arises. If the FBI didn’t find the server because of a leaky CAPTCHA, how did it find a PHPMyAdmin page instead?